Limit switch

ABSTRACT

A limit switch in which an actuating head is mounted on the housing. Electrical switches are mounted in the housing, without fasteners, by means of a removable support structure. Eccentric adjustment members are provided for adjusting the amount of pretravel of the switch actuating mechanism. A terminal block is provided which both aids in supporting the switches and provides means for making external connection to them.

United States Patent [72] Inventors Martin D. Ustin Union; Edward W;Baumgartner, lrvington, both of, NJ.

[21] Appl. No. 833,018

[22] Filed June 13, 1969 [45] Patented June 29, 1971 [73] AssigneeBuchanan Electrical Products Corporation Union, NJ.

[54] LIMIT SWITCH 24 Claims, 8 Drawing Figs.

[51] lnt.Cl ...H0lh 21/28 [50] Field of Search 200/47, 166 CT, 6 B, 6 A

[56] References Cited UNITED STATES PATENTS 3,097,271 7/1963 Denison.1200/166 x ITCS 3,257,856 6/1966 Parns, Jr 200/47 X 3,275,764 9/1966Kiessling et a1. 200/47 3,287,516 11/1966 Nielsen 200/47 3,303,2982/1967 Dobes 200/47 3,306,997 2/1967 Jacobs... 200/47 3.317.687 5/1967Dehn 200/47 Primary Examiner-Robert K. Schaefer Assistant Examiner-H. J.l-lohauser Attorney-Curtis, Morris and Safford ABSTRACT: A limit switchin which an actuating head is mounted on the housing. Electricalswitches are mounted in the housing, without fasteners, by means of aremovable support structure. Eccentric adjustment members are providedfor adjusting the amount of pretravel of the switch actuating mechanism.A terminal block is provided which both aids in supporting the switchesand provides means for making external connection to them.

LIMIT SWITCH This invention relates to electrical switches, andparticularly to electrical limit switches.

A limit switch typically is used to stop a mechanical movement byturning off the energization to a drive motor which is causing themovement. For example, the switch often is positioned near a machine tolimit the movement of a cutting tool. The limit switch usually has anactuating arm or plunger with a roller on it. When a machine componentcontacts the roller and depresses the plunger or rotates the arm, thismechanical movement opens or closes an electrical switch so as to stopor limit the movement of the machine component.

One problem with prior limit switches is that often it is difficult andslow to change the electrical switch which is mounted in the housing ofthe limit switch device. Furthermore, in certain prior art limitswitches, the electrical switch is mounted on the same portion of thelimit switch structure as is the head which carries the actuating arm.As a result, in order to obtain a fair degree of speed in changing theelectrical switch, it has been customary to change the entire portion ofthe device which includes both the electrical switch and the actuatinghead. The disadvantage of this procedure is that the new head probablywill not be set to the position of the old head so that the new headmust be adjusted before it can be used. Thus, the switch-changingprocess is slowed even further.

Another problem with prior limit switchs is that it often is difficultand time-consuming to change the amount of pretravel of the switch; thatis, the distance which the plunger or actuating arm must move before theelectrical switch is actuated.

Still another problem with prior limit switches is that it often isdifficult to secure external wires to the wiring terminals in theswitching device. Also, it often is complicated to connect theelectrical switches to the wiring terminals.

In accordance with the foregoing, it is an object of the presentinvention to provide a limit switch device in which the electricalswitches can be changed relatively rapidly and easily. It is a furtherobject of the present invention to provide such a device in which theamount of pretravel of the actuating mechanism can be adjusted rapidlyand easily. It is another object of the present invention to providesuch a device which is easy to wire and to which it is easy to connectand mount an electrical switch.

In accordance with the present invention, the foregoing objects are metby the provision of a limit switch in which the actuating head issecured to the housing. Electrical switches are mounted in the housing,without fasteners, by means of a removable support structure. Eccentricadjustment members which are accessible from a front opening in thehousing are provided for adjusting the amount of pretravel of the switchactuating mechanism. A wiring and terminal block is provided formounting the switches and for easily connecting wires thereto. 7

Further objects and advantages of the invention will be either pointedout in or apparent from the following description and drawings. In thedrawings:

FIG. 1 is an exploded perspective view of one embodiment of the presentinvention;

FIG. 2 is a partially schematic cross-sectional view taken along line2-2 of FIG. 1;

FIG. 3 is a partially cross-sectional view of a component of theswitching device shown in FIGS. I and 2;

FIG. 4 is a partially cross-sectional view of a component of a deviceshown in FIGS. I through 3;

FIGS. 5, 6 and 7 are cross-sectional views of the actuating heads ofthree further embodiments of the present invention; and

FIG. 8 is a cross-sectional view of a component of one embodiment of theinvention.

GENERAL DESCRIPTION Referring first to FIG. I, the limit switch device10 includes a housing 12, a turret or actuating head 14 rotatablymounted on the housing 12, and an arm 18 with a roller 20 at one end.The arm 18 is secured to a shaft 16 which is rotatably mounted in theturret I4. Rotation of the shaft 16 by means of the arm 18 causes aplunger 50 (FIG. 2) to be depressed.

Two electrical switches 22 and 24 are mounted in the housing 12 and arepositioned (See FIG. 2) so that when the plunger 50 is depresseddownwardly, it depresses a switch-actuating member 36 which in turndepresses switch buttons 25 on the switches 22 and 24, thus actuatingthe switches. Wires 34 enter the bottom of the housing through a conduit35 and are connected to a terminal block 26 which is mounted in thehousing 12. Each switch has four blade-shaped electrical contacts 23which fit into receptacles in the terminal block 26 and thus areconnected to the wires 34, and thence to a control circuit (not shown)to limit the motion of the object which hits the arm 18, or to performother control functions.

THE TURRET The turret 14 is made in two halves 60 and 62 which arefastened together by means of a pair of screws 65 (see FIG. 1 As isshown in FIG. 2, the turret 14 can be rotated to any position within afull circle by means of a worm 58 which meshes with gear teeth 59 cutinto the lower edge of the generally cylindrically shaped turret 14. Byturning the worm 58 with a screwdriver, the rotary position of theturret 14 can be adjusted as desired so as to accommodate the limitswitch to actuation in a multitude of different positions.

The actuating mechanism can be adjusted to operate in three differentmodes; only with clockwise motion of the arm 18, or only withcounterclockwise motion, or with both clockwise and counterclockwisemotion of the arm 18. Adjustment to one or the other of these modes iseffected by first lifting a flexible protective covering 44, and thendepressing a spring-loaded plunger 46 (with a screwdriver or the like)so as to disengage a latch member 47 from one of three notches 48 whichnormally holds the shaft 16 in a particular longitudinal position. Then,the shaft 16 is either pulled or pushed longitudinally to a newposition, the plunger 46 is released, and the spring return for thelatch member 47 engages it in a different notch 48.

Two mirror-image cams 40 and 42 are attached to the shaft 16. A roller52 is attached to the upper end of plunger 50. The cams 40 and 42 areshaped so that when the shaft 16 is in its rest position, neither camdepresses the roller. However, when the latch member 47 is in the middleone of the three notches 48, rotation of the arm 18 in either theclockwise or counterclockwise direction will cause one of the cams 40 or42 to engage the roller 52, thus causing depression of the plunger 50and actuation of the switches 22 and 24.

With the latch member 47 in the left one of the three notches 48, theroller 52 will engage only the cam 40, and the plunger 50 will bedepressed only by rotation of the shaft 16 in one direction. When thelatch member 47 is in the right one of the three notches, only the cam42 will engage the roller 52 and the plunger 50 will be depressed uponrotation of the shaft only in the other of the two directions.

A member 54 with a flat lower surface bears against a flat cutoutportion in the shaft 16 under the pressure of a pair of coil springs 56.This provides means for returning the arm 18 to its initial restposition. Each of the actuating buttons 25 of the switches 22 and 24 isspring-loaded, and this spring loading returns the plunger 50 to itsuppermost position when the switch actuation movement is completed.Further details regarding the operation of this mechanism are given inapplication Ser. No. 567,172 filed on July 22, 1966, and assigned to thesame assignee as this patent application. The disclosure of that patentapplication hereby is incorporated herein by reference.

3 TI-IE ADJUSTABLE SWITCH ACTUATING MEMBER slotted head and can. bedriven by a screwdriver to rotate it to a new position. Each projectionthus is positioned either relatively closer to or farther away from oneof the switch buttons 25 so as to'provide means for adjustment of theamount of pretr'aver' of theactu ating mechanism.

The surfaces of the body 36 which bear against the mating edges of theprojections 37 and 39 are serrated as shown-at 43 in FIG. 3. Theprojections 37 and 39 have two teeth which engage the serrations inorder to provide means for'holding the projection 37 or 39 in a positionto which it is moved. The body of member 36 preferably is made out of aninsulating plastic material such as nylon, and the projections 37 and 39advantageously are made out of another insulating material suchas thatsold under the trademark -Delrin."

TERMINAL COVER AND SWITCH MOUNTING MEANS Referring again to FIG. 1, aninsulating cover 28 fits into the housing to cover the terminal blockand to assist in supporting the switches 22 and 24 in the housing 12. Acover 30 and a gasket 32 are secured to the housing by means of screws31 to provide an oiltight cover for the housing.

In accordance with another feature of the present invention, theterminal cover 28 is used to assist in supporting the electricalswitches 22 and 24, as well asto cover the terminal block ridge 69around the edges of the locations of the switches helps to insulate theswitches.

.T he innermost end of the blades 23 of the switches 22 and 24 extendinto and are held by the terminal block 26 (See FIG.

4). This assists in holding the switches in place..

THE TERMINAL BLOCK As in shown in FIG. 4, the terminal block 26 includesa body 73 made of nonconductive material such as plastic in which aremounted several short tubes 74 having a rectangular crosssectionalshape. These tubes are made out of a conductive metal such as copper.Fitted into one sidewall of each tube 74 is a screw 76. Screw 76 has anenlarged inner end 80 which bears against the bare end of one of thewires 34 so as to hold the wire in place and in contact with the metaltube 74. A conductive spring metal clip 82 engages the outside of eachtube 74. Each member 82 has a curved portion 75 which acts to hold oneof the blades 23 in contact with one of the tubes 74.

Thus, when one of the blades is inserted through the holes 72 in theterminal block cover 28, the switch is supported at two points; at thepoint where it contacts the material of the cover plate 28, and also atthe point where the blade makes contact with the clip 82 and one of themetal tubes 74. Thus, mounting means on the housing 12 or cover 30 arenot required.

The foregoing arrangement is particularly simple to use and convenientin that the wires 34 can be connected to the terminal block simply byinserting their ends in the tubes 74 and tightening the screws 76. Thespring ,clips 82 provide an easy and simple means of simultaneouslysupporting the switches and making electricalcontact between the wires34 and the switch blades 23.

Another advantage of the present invention is that the amount ofpretravel of the switch easily can be adjusted by simply removing thecover 30, inserting a screwdriver into the slots in the heads of theprojections 37 and 39, and then turnthem with other switches. No toolsare necessary. Screws and bolts are not needed to hold the switches inplace.

SIDE-ACTUATED SWITCH FIG. 5 shows the actuating head or turret ofanother limit switch constructed in accordance with the present invention. The remainder of this limit switch is the same as is shown inFIGS. 1 through 4 andis not shown in FIG. 5 for the sake of simplicityin the drawings.

The turret 100 is formed of two halves 101 and 103, and has a shaft 102slidably mounted in the turret and extending in a directionperpendicular to the axis of the plunger 50. The shaft 102 has a groove104 into which is fitted a retaining ring 108. Shaft 102 has a section109 with two flats cut on it, and a cylindrical right end portion 111 ofa diameter smaller than that of the left end. A spring retainer cup witha rectangular external shape fits onto the flats of section 109, and acoil spring 112 fits into the cup and thrusts the cup against theretaining ring 108. The ring 108 abuts a ridge 106 to stop its movementtowards the left.

The cup 110 has a beveled edge 116 which abuts the beveled edge of a cam118 fastened to the upper end of plunger 50. When the shaft 102 ispressed inwardly, it slides in bearings 105 and 114, and the bevelededge 116 forces the cam 118 and slides plunger 50 downwardly in bearing120 to operate the switches. Two of the edges of the cup are beveled asshown at 1 16 in order to facilitate the use of a roller on the end ofshaft 102. As in the embodiment shown in FIGS;11 through 4, the turret100 is rotatable so that it can be actuated from many differentdirections. The internal shape of the turret is such that it engages therectangularly-shaped outside of cup member 110 to keep it from rotatingin the turret.

TOP ACTUATED SWITCH FIG. 6 shows the turret of another embodiment of theinvention. Again, as in FIG. '5, the remainder of the limit switch isnot shown in order to simplify the drawings.

The turret 130 has two halves 132 and 134, and has a depressableactuating button 136 extending vertically from its top. The lowerportion of button 136 is secured to a spring retainer cup 138, which isfunctionally similar to the cup 110 shown in FIG. 5. A coil spring 140fits into the cup 138. The external shape of the cup is such that itwill not rotate in the housing. The plunger 50 has a reduced crosssection with spring retainer cups 146 and 148 and a small coil spring150 surrounding the reduced portion of the plunger. The top portion ofthe plunger fits into a hole 144 in the bottom portion of the button136. v

When the button 136 is depressed, the spring 140 is compressed and theplunger 50 is depressed until the switches have been actuated. Shortlythereafter, the bottom retainer 148 for the small spring hits the insidebottom wall of the housing 134. From then on, further depression of thebutton 136 does notdepress the plunger 50 any further; instead, thespring 150 compresses and the top 145 of plunger 50 moves up into thehole 144. Thus, the motion of the plunger 50 is limited to thatnecessary to actuate the switches.

UNIVERSALLY ACTUATED SWITCH FIG. 7 shows the turret of another switchembodiment of the present invention. Its operation is the same as thatof the switch shown in FIG. 6, except that a universal" actuating lever166 replaces the button 136.

Lever 166 is secured to a hemispherical member 168 which is movablymounted in a bearing structure 170. A cover 172 made of rubber, flexibleplastic or other. suitable flexible material is fitted around the balljoint and the lever 166. When the lever 166 is pushed from the side, itpivots about the ball joint and the lower edge of the hemisphere 168depresses a ring 169 which depresses the cup 138 to push the plunger 50downwardly and actuate the switches in the housing, as in the FIG. 6embodiment. The lever 166 can be actuated from almost any direction. Twoof the positions to which it can be shifted are shown in dashed outlinein FIG. 7.

, ROLLERS Another advantageous feature of the invention is shown inFIG. 1. The roller 20 is fastened to the arm 18 by means of aself-tapping screw 21. Thus, the user of the'limit switch can selectamong a number of different roller sizes and types and can attach theroller himself.

Another advantageous roller construction is shown in FIG. 8. The roller200 is composed of an inner core 206 made of a plastic such as Nylon,and an outer metal ring 204 tightly fitted onto the core. The core 206is rotatably mounted on a hub 202 extending from the actuating arm 18. Ascrew 208 is threaded intoa hole in the hub 202 to hold the roller 200in place. The nylon core can be used alone as a roller, or, if a hardersurface or a larger diameter is required, the user can add the ring 204to the core 206. The composite roller 200 is lighter than would be asolid metal roller of the same size.

The above description of the invention is intended to be illustrativeand not limiting. Various changes or modifications in the embodimentsdescribed may occur to those skilled in the art and these can be madewithout departing from the spirit or scope of the invention.

We claim:

1. An electrical limit switch device comprising a housing adapted to bemounted on a support structure, a removable cover for said housing, anelectrical switch having contact projections, an actuating member insaid housing for actuating said switch in response to being driven by anactuating motion, wiring terminal means in said housing, and switchsupport means for selectively insulating said switch from said terminalmeans for supporting said switch with its contact projections engagingsaid terminal means with said switch in position to be actuated bymovement of said actuating member, said support means being removablefrom said housing and separate from said cover.

2. Apparatus as in claim 1 in which said switch support means includesan insulating plate with apertures through which said projections extendand a ledge for supporting said switch against the force of saidactuating member, and resilient gripping means in said terminal means.

3. Apparatus as in claim 2 in which said resilient gripping means formsa conductive receptacle for connecting a wire to one of said switchcontact projections.

4. An electrical limit switch device comprising a housing adapted to bemounted on a support structure, an electrical switch in said housing, anactuating member in said housing for actuating said switch in responseto being driven by an actuating motion, means for adjusting the lengthof travel of said actuating member before it actuates said switch, saidmeans including a rotatable spacer member on said actuating member, saidspacer member being assymetiic about its axis of rotation to providedifferent amounts of spacing in different ones of its rotationalpositions.

5. Apparatus as in claim 4 including a removable coverfor said housing,said rotatable spacer member having a head shaped to receive a rotarydriving tool, said spacer member being positioned to be drivable by sucha tool when the latter is inserted through the opening in said housingwhich is left when said cover is removed.

6. Apparatus as in claim 4 in which said spacer member is positioned andmounted to be movable in a direction transverse to said axis of rotationin order to actuate said switch.

7. An electrical limit switch device comprising a housing adapted to bemounted on a support structure, an electrical switch having contactprojections, wiring terminal means in said housing, said wiring terminalmeans having a plurality of conductive tubular members, a clampingmember extending into each such tube through a sidewall of said tube togrip a wire therein, a conductive spring clip around the outside of eachsuch tubular member, with said contact projections of said switchesbeing clamped between said clips and said tubular members.

8. Apparatus as in claim 7 in which each of said tubular members has arectangular cross-sectional shape.

9. Apparatus as in claim 7 including a removable cover for said housing,and in which said clamping member comprises a threaded screw, anddriving tool-engaging means in the head of said screw, with said screwhead facing towards said cover.

10. Apparatus as in claim 1 including an arm secured to a shaft, aturret rotatably mounted on said housing, with said shaft rotatablymounted in said turret, and means drivably coupling said shaft to saidactuating member.

11. An electrical limit switch device comprising a housing, a turretrotatably mounted on said housing, a worm and mating gear engagedtogether to rotate said turret with respect to said housing, anelectrical switch in said housing, an actuating member in said housingfor actuating said switch in response to being driven by an actuatingmotion, a push member extending out from said turret and depressable tomove said actuating member, and spring return means for said pushmember.

12. Apparatus as in claim 11 in which said push member is mounted tomove in the same direction as said actuating member.

13. Apparatus as in claim 11 in which said push member is mounted tomove in a direction perpendicular to the direction of motion of saidactuating member, and including cam means for drivably coupling saidpush member to said actuating member.

14. Apparatus as in claim 11 including additional spring means forlimiting the movement of said actuating member to a predetermineddistance without so limiting the movement of said plunger.

15. An electrical limit switch device comprising a housing, a memberextending out of said housing and engageable to actuate a switch in saidhousing, spring return means for returning said member to its disengagedposition, a plunger drivable by said member to actuate said switch, andspring means for limiting the movement of said plunger to apredetermined distance without so limiting the movement of said member.

16. Apparatus as in claim 15 in which said member is a lever mounted onsaid housing by a ball joint, and means for translating pivotal movementof said lever into movement of said plunger.

17. Apparatus as in claim 15 in which said member is a pushbuttonslidable in the direction of said plunger.

18. Apparatus as in claim 5 in which serrations are located between saidcontact member and said actuating member.

19. Apparatus as in claim 5 including a plurality of said switches, anda plurality of said contact members on said actuating member, therebeing one contact member per switch.

20. An electrical limit switch device comprising a housing adapted to bemounted on a support structure, a removable cover for said housing, anelectrical switch having contact projections, an actuating member insaid housing for actuating said switch in response to being driven by anactuating motion, wiring terminal means in said housing, switch supportmeans removable from said housing and separate from said cover forsupporting said switch with its contact projections engaging saidterminal means with said switch in position to be actuated by movementof said actuating member, an arm secured to a shaft, a turret rotatablymounted on said housing, with said shaft rotatably mounted in saidturret, means drivably coupling said shaft to said actuating member, aroller on said arm, said roller having a nonmetallic core fitted into ametallic ring, said ring forming the outer periphery of said roller.

I matching the internal contours of said housing, the externaldimensions of said support member being smaller than the internaldimensions of said housing by a relatively small amount so that saidsupport member fits into and supports itself in said housing, saidsupport member having means for supporting said switch with'its contactprojections engaging said terminal means with said-switch in position tobe actuated by movement of said actuating member.

22. A limit switch as in claim 21 in which said support member comprisesan insulating plate with apertures through which said projections extendand a ledge for supporting said switch against the force of saidactuating member, and resilient gripping means in said terminal means.

23,. A limit switch as in claim 21 in which said support member includesa guide for guiding the movement of said actuating member.

24. A limit switch as in claim in which the movementlimiting springmeans includes a compression spring extending around said plunger, apair of abutments on said plunger for limiting the expansion of saidcompression spring, and means for normally holding one end of saidcompression spring against said member with the other end spaced from astop structure by a predetermined distance, both ends of saidcompression spring being free to move on said plunger during compressionof said spring.

1. An electrical limit switch device comprising a housing adapted to bemounted on a support structure, a removable cover for said housing, anelectrical switch having contact projections, an actuating member insaid housing for actuating said switch in response to being driven by anactuating motion, wiring terminal means in said housing, and switchsupport means for selectively insulating said switch from said terminalmeans for supporting said switch with its contact projections engagingsaid terminal means with said switch in position to be actuated bymovement of said actuating member, said support means being removablefrom said housing and separate from said cover.
 2. Apparatus as in claim1 in which said switch support means includes an insulating plate withapertures through which said projections extend and a ledge forsupporting said switch against the force of said actuating member, andresilient gripping means in said terminal means.
 3. Apparatus as inclaim 2 in which said resilient gripping means forms a conductivereceptacle for connecting a wire to one of said switch contactprojections.
 4. An electrical limit switch devicE comprising a housingadapted to be mounted on a support structure, an electrical switch insaid housing, an actuating member in said housing for actuating saidswitch in response to being driven by an actuating motion, means foradjusting the length of travel of said actuating member before itactuates said switch, said means including a rotatable spacer member onsaid actuating member, said spacer member being assymetric about itsaxis of rotation to provide different amounts of spacing in differentones of its rotational positions.
 5. Apparatus as in claim 4 including aremovable cover for said housing, said rotatable spacer member having ahead shaped to receive a rotary driving tool, said spacer member beingpositioned to be drivable by such a tool when the latter is insertedthrough the opening in said housing which is left when said cover isremoved.
 6. Apparatus as in claim 4 in which said spacer member ispositioned and mounted to be movable in a direction transverse to saidaxis of rotation in order to actuate said switch.
 7. An electrical limitswitch device comprising a housing adapted to be mounted on a supportstructure, an electrical switch having contact projections, wiringterminal means in said housing, said wiring terminal means having aplurality of conductive tubular members, a clamping member extendinginto each such tube through a sidewall of said tube to grip a wiretherein, a conductive spring clip around the outside of each suchtubular member, with said contact projections of said switches beingclamped between said clips and said tubular members.
 8. Apparatus as inclaim 7 in which each of said tubular members has a rectangularcross-sectional shape.
 9. Apparatus as in claim 7 including a removablecover for said housing, and in which said clamping member comprises athreaded screw, and driving tool-engaging means in the head of saidscrew, with said screw head facing towards said cover.
 10. Apparatus asin claim 1 including an arm secured to a shaft, a turret rotatablymounted on said housing, with said shaft rotatably mounted in saidturret, and means drivably coupling said shaft to said actuating member.11. An electrical limit switch device comprising a housing, a turretrotatably mounted on said housing, a worm and mating gear engagedtogether to rotate said turret with respect to said housing, anelectrical switch in said housing, an actuating member in said housingfor actuating said switch in response to being driven by an actuatingmotion, a push member extending out from said turret and depressable tomove said actuating member, and spring return means for said pushmember.
 12. Apparatus as in claim 11 in which said push member ismounted to move in the same direction as said actuating member. 13.Apparatus as in claim 11 in which said push member is mounted to move ina direction perpendicular to the direction of motion of said actuatingmember, and including cam means for drivably coupling said push memberto said actuating member.
 14. Apparatus as in claim 11 includingadditional spring means for limiting the movement of said actuatingmember to a predetermined distance without so limiting the movement ofsaid plunger.
 15. An electrical limit switch device comprising ahousing, a member extending out of said housing and engageable toactuate a switch in said housing, spring return means for returning saidmember to its disengaged position, a plunger drivable by said member toactuate said switch, and spring means for limiting the movement of saidplunger to a predetermined distance without so limiting the movement ofsaid member.
 16. Apparatus as in claim 15 in which said member is alever mounted on said housing by a ball joint, and means for translatingpivotal movement of said lever into movement of said plunger. 17.Apparatus as in claim 15 in which said member is a pushbutton slidablein the direction of said plunger.
 18. Apparatus as in claim 5 in whichserrations are located between saId contact member and said actuatingmember.
 19. Apparatus as in claim 5 including a plurality of saidswitches, and a plurality of said contact members on said actuatingmember, there being one contact member per switch.
 20. An electricallimit switch device comprising a housing adapted to be mounted on asupport structure, a removable cover for said housing, an electricalswitch having contact projections, an actuating member in said housingfor actuating said switch in response to being driven by an actuatingmotion, wiring terminal means in said housing, switch support meansremovable from said housing and separate from said cover for supportingsaid switch with its contact projections engaging said terminal meanswith said switch in position to be actuated by movement of saidactuating member, an arm secured to a shaft, a turret rotatably mountedon said housing, with said shaft rotatably mounted in said turret, meansdrivably coupling said shaft to said actuating member, a roller on saidarm, said roller having a nonmetallic core fitted into a metallic ring,said ring forming the outer periphery of said roller.
 21. An electricallimit switch device comprising a housing adapted to be mounted on asupport structure, a removable cover for said housing, an electricalswitch having contact projections, an actuating member in said housingfor actuating said switch in response to being driven by an actuatingmotion, wiring terminal means secured to and within said housing, aswitch support member having external contours generally matching theinternal contours of said housing, the external dimensions of saidsupport member being smaller than the internal dimensions of saidhousing by a relatively small amount so that said support member fitsinto and supports itself in said housing, said support member havingmeans for supporting said switch with its contact projections engagingsaid terminal means with said switch in position to be actuated bymovement of said actuating member.
 22. A limit switch as in claim 21 inwhich said support member comprises an insulating plate with aperturesthrough which said projections extend and a ledge for supporting saidswitch against the force of said actuating member, and resilientgripping means in said terminal means.
 23. A limit switch as in claim 21in which said support member includes a guide for guiding the movementof said actuating member.
 24. A limit switch as in claim 15 in which themovement-limiting spring means includes a compression spring extendingaround said plunger, a pair of abutments on said plunger for limitingthe expansion of said compression spring, and means for normally holdingone end of said compression spring against said member with the otherend spaced from a stop structure by a predetermined distance, both endsof said compression spring being free to move on said plunger duringcompression of said spring.